Devices for ejecting moldings from injection molding machines are known. For example, Federal Republic of Germany Application No. OS 35 42 878 discloses an ejection device for injection molding machines in which hydraulically actuatable ejector pins are arranged on an ejector plate. However, the ejector pins are fastened in this connection to the ejector device by screw attachments on the piston of a hydraulic drive. Accordingly, this detachable screw connection does not suggest the use of an easily separable connection without manual intervention. Moreover, to unscrew this connection the complete dismounting stroke is required.
European Patent OS 02 33 113 discloses a coupling for an ejection device in which a piston-shaped rod can be inserted into a sleeve and held in a purely form-locked manner by radially displaceable pins. With this device, the entire distance corresponding to the overlapping male and female parts is required for the decoupling action. Additionally, the purely form-locked connection of the coupling has the disadvantage that a certain amount of play is present between the structural parts to be connected and that the coupling bar may possibly turn relative to the piston rod.
None of the prior art, however, teaches or suggests an apparatus for ejecting a molding from an injection molding machine with an ejection device having a compact coupling which permits a play-free transmission of force, which is easily separated and which does not require a travel path beyond the ejector stroke on the machine side.
It is, therefore, an object of this invention to provide an apparatus for ejecting moldings from an injection molding machine having an easily separable connection.
Another object of the invention is to provide an ejection machine which permits play free transmission of force.
A further object of the invention is to provide a connection that, for the decoupling thereof, does not require a travel path or distance beyond the ejector stroke on the machine side.
Still other objects and advantages of the invention will be apparent from the specification.
The ejector of the present invention includes a coupling sleeve having an inner surface which converges toward the head end of the coupling rod. The coupling sleeve is, in this connection, preferably fastened to the mold base plate and is arranged in an axial direction so that it extends only slightly and thus, without hinderance into the free space between the mold base plate and the ejector device.
The head of the coupling rod is insertable into the coupling sleeve. The coupling rod has, at its head end, a telescopically extendible rod, the end of which is dimensioned so as to fit closely into the coupling sleeve. The drive for the lateral movement of the coupling rod is preferably hydraulically actuated by utilizing the hydraulic system which is ordinarily present.
In a coupled condition, radially outwardly forces are applied to the front part of the coupling rod. These forces, beyond providing a mating fit between the coupling rod and the sleeve, permit clamping forces to act therebetween. These forces are substantial, since a relatively large piston surface is available. In this fashion, a form-locked (mechanical interference fit) and a force-locked (frictional fit) connection are obtained in a structurally simple manner by an actuating rod which is introduced centrally into the sleeve-shaped coupling member.
The tip or head region of the actuating rod is conically pointed and corresponds to the head region of the sleeve-shaped coupling rod which, preferably, also has a conical shape due to having a wall thickness which increases radially inwardly. Preferably, slits extending in the axial direction are provided in the head of the coupling rod to facilitate the increase of the diameter of the coupling rod head. After the head of the coupling rod is inserted into the coupling sleeve on the ejector plate, radially outwardly directed forces are applied by the movement of the actuating rod head region relative to the coupling rod head region in order to form the above-mentioned form-locked and force-locked connection.
In the coupled condition, the head ends of the coupling rod and actuating rod are connected in form-locked and force-locked manner with the coupling sleeve so that all coupling play is prevented. Therefore, with simple construction, high reliability in operation is obtained. Furthermore, this construction allows for the high reproducibility or repeatability of the coupling process.
In contrast to comparable ejectors of prior art injection molding machines in which the main piston is used for the coupling operation, the adjustable or reciprocatingly moveable coupling of the present invention prevents the loss of travel path or distance of travel in the region of the end-position of the opening phase of the ejector device. In this connection, the rear region, namely the space between the bottom of the main cylinder and the base surface of the main piston is particularly important and necessary for the end position damping of the ejector.
An actuating rod can furthermore also be arranged alongside of the actuating piston with the actuating rod in the coupled position, permitting a simple loosening of the coupling piston from the actuating piston.
Additionally, the tubular coupling rod is preferably radially divisible and provided with an annular chamber. An annular piston which is axially movable in the annular chamber is provided on the actuating rod.